time/tzset.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <ctype.h>
  20 #include <stddef.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <time.h>
  25
  26 /* Defined in mktime.c.  */
  27 extern const unsigned short int __mon_yday[2][13];
  28
  29 #define NOID
  30 #include "tzfile.h"
  31
  32 extern int __use_tzfile;
  33 extern void __tzfile_read __P ((const char *file));
  34 extern void __tzfile_default __P ((char *std, char *dst,
  35                                    long int stdoff, long int dstoff));
  36 extern int __tz_compute __P ((time_t timer, const struct tm *tm));
  37
  38 char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
  39 int __daylight = 0;
  40 long int __timezone = 0L;
  41
  42 weak_alias (__tzname, tzname)
  43 weak_alias (__daylight, daylight)
  44 weak_alias (__timezone, timezone)
  45
  46
  47 #define min(a, b)       ((a) < (b) ? (a) : (b))
  48 #define max(a, b)       ((a) > (b) ? (a) : (b))
  49 #define sign(x)         ((x) < 0 ? -1 : 1)
  50
  51
  52 /* This structure contains all the information about a
  53    timezone given in the POSIX standard TZ envariable.  */
  54 typedef struct
  55   {
  56     char *name;
  57
  58     /* When to change.  */
  59     enum { J0, J1, M } type;    /* Interpretation of:  */
  60     unsigned short int m, n, d; /* Month, week, day.  */
  61     unsigned int secs;          /* Time of day.  */
  62
  63     long int offset;            /* Seconds east of GMT (west if < 0).  */
  64
  65     /* We cache the computed time of change for a
  66        given year so we don't have to recompute it.  */
  67     time_t change;      /* When to change to this zone.  */
  68     int computed_for;   /* Year above is computed for.  */
  69   } tz_rule;
  70
  71 /* tz_rules[0] is standard, tz_rules[1] is daylight.  */
  72 static tz_rule tz_rules[2];
  73
  74
  75 static int compute_change __P ((tz_rule *rule, int year));
  76 \f
  77 int __tzset_run = 0;
  78
  79 /* Interpret the TZ envariable.  */
  80 void
  81 __tzset ()
  82 {
  83   register const char *tz;
  84   register size_t l;
  85   unsigned short int hh, mm, ss;
  86   unsigned short int whichrule;
  87
  88   /* Free old storage.  */
  89   if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
  90     {
  91       free((void *) tz_rules[0].name);
  92       tz_rules[0].name = NULL;
  93     }
  94   if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
  95       tz_rules[1].name != tz_rules[0].name)
  96     {
  97       free((void *) tz_rules[1].name);
  98       tz_rules[1].name = NULL;
  99     }
 100
 101   /* Examine the TZ environment variable.  */
 102   tz = getenv ("TZ");
 103
 104   /* A leading colon means "implementation defined syntax".
 105      We ignore the colon and always use the same algorithm:
 106      try a data file, and if none exists parse the 1003.1 syntax.  */
 107   if (tz && *tz == ':')
 108     ++tz;
 109
 110   /* Try to read a data file.  */
 111   __tzfile_read (tz);
 112   if (__use_tzfile)
 113     {
 114       __tzset_run = 1;
 115       return;
 116     }
 117
 118   /* No data file found.  Default to UTC if nothing specified.  */
 119
 120   if (tz == NULL || *tz == '\0')
 121     {
 122       static const char UTC[] = "UTC";
 123       size_t len = sizeof UTC;
 124       tz_rules[0].name = (char *) malloc(len);
 125       if (tz_rules[0].name == NULL)
 126         return;
 127       tz_rules[1].name = (char *) malloc(len);
 128       if (tz_rules[1].name == NULL)
 129         return;
 130       memcpy ((void *) tz_rules[0].name, UTC, len);
 131       memcpy ((void *) tz_rules[1].name, UTC, len);
 132       tz_rules[0].type = tz_rules[1].type = J0;
 133       tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
 134       tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
 135       tz_rules[0].secs = tz_rules[1].secs = 0;
 136       tz_rules[0].offset = tz_rules[1].offset = 0L;
 137       tz_rules[0].change = tz_rules[1].change = (time_t) -1;
 138       tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
 139       __tzset_run = 1;
 140       return;
 141     }
 142
 143   /* Clear out old state and reset to unnamed UTC.  */
 144   memset (tz_rules, 0, sizeof tz_rules);
 145   tz_rules[0].name = tz_rules[1].name = (char *) "";
 146
 147   /* Get the standard timezone name.  */
 148   tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
 149   if (tz_rules[0].name == NULL)
 150     /* Don't set __tzset_run so we will try again.  */
 151     return;
 152
 153   if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
 154       (l = strlen(tz_rules[0].name)) < 3)
 155     {
 156       free (tz_rules[0].name);
 157       tz_rules[0].name = (char *) "";
 158       return;
 159     }
 160
 161   {
 162     char *n = realloc ((void *) tz_rules[0].name, l + 1);
 163     if (n != NULL)
 164       tz_rules[0].name = n;
 165   }
 166
 167   tz += l;
 168
 169   /* Figure out the standard offset from UTC.  */
 170   if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
 171     return;
 172
 173   if (*tz == '-' || *tz == '+')
 174     tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
 175   else
 176     tz_rules[0].offset = -1L;
 177   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 178     {
 179     default:
 180       return;
 181     case 1:
 182       mm = 0;
 183     case 2:
 184       ss = 0;
 185     case 3:
 186       break;
 187     }
 188   tz_rules[0].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 189                          (min (hh, 23) * 60 * 60));
 190
 191   for (l = 0; l < 3; ++l)
 192     {
 193       while (isdigit(*tz))
 194         ++tz;
 195       if (l < 2 && *tz == ':')
 196         ++tz;
 197     }
 198
 199   /* Get the DST timezone name (if any).  */
 200   if (*tz != '\0')
 201     {
 202       char *n = malloc (strlen (tz) + 1);
 203       if (n != NULL)
 204         {
 205           tz_rules[1].name = n;
 206           if (sscanf (tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
 207               (l = strlen (tz_rules[1].name)) < 3)
 208             {
 209               free (n);
 210               tz_rules[1].name = (char *) "";
 211               goto done_names;  /* Punt on name, set up the offsets.  */
 212             }
 213           n = realloc ((void *) tz_rules[1].name, l + 1);
 214           if (n != NULL)
 215             tz_rules[1].name = n;
 216
 217           tz += l;
 218         }
 219     }
 220
 221   /* Figure out the DST offset from GMT.  */
 222   if (*tz == '-' || *tz == '+')
 223     tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
 224   else
 225     tz_rules[1].offset = -1L;
 226
 227   switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 228     {
 229     default:
 230       /* Default to one hour later than standard time.  */
 231       tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
 232       break;
 233
 234     case 1:
 235       mm = 0;
 236     case 2:
 237       ss = 0;
 238     case 3:
 239       tz_rules[1].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
 240                              (min (hh, 23) * (60 * 60)));
 241       break;
 242     }
 243   for (l = 0; l < 3; ++l)
 244     {
 245       while (isdigit (*tz))
 246         ++tz;
 247       if (l < 2 && *tz == ':')
 248         ++tz;
 249     }
 250
 251  done_names:
 252
 253   if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
 254     {
 255       /* There is no rule.  See if there is a default rule file.  */
 256       __tzfile_default (tz_rules[0].name, tz_rules[1].name,
 257                         tz_rules[0].offset, tz_rules[1].offset);
 258       if (__use_tzfile)
 259         {
 260           __tzset_run = 1;
 261           return;
 262         }
 263     }
 264
 265   /* Figure out the standard <-> DST rules.  */
 266   for (whichrule = 0; whichrule < 2; ++whichrule)
 267     {
 268       register tz_rule *tzr = &tz_rules[whichrule];
 269
 270       if (*tz == ',')
 271         {
 272           ++tz;
 273           if (*tz == '\0')
 274             return;
 275         }
 276
 277       /* Get the date of the change.  */
 278       if (*tz == 'J' || isdigit (*tz))
 279         {
 280           char *end;
 281           tzr->type = *tz == 'J' ? J1 : J0;
 282           if (tzr->type == J1 && !isdigit (*++tz))
 283             return;
 284           tzr->d = (unsigned short int) strtoul (tz, &end, 10);
 285           if (end == tz || tzr->d > 365)
 286             return;
 287           else if (tzr->type == J1 && tzr->d == 0)
 288             return;
 289           tz = end;
 290         }
 291       else if (*tz == 'M')
 292         {
 293           int n;
 294           tzr->type = M;
 295           if (sscanf (tz, "M%hu.%hu.%hu%n",
 296                       &tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
 297               tzr->m < 1 || tzr->m > 12 ||
 298               tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
 299             return;
 300           tz += n;
 301         }
 302       else if (*tz == '\0')
 303         {
 304           /* United States Federal Law, the equivalent of "M4.1.0,M10.5.0".  */
 305           tzr->type = M;
 306           if (tzr == &tz_rules[0])
 307             {
 308               tzr->m = 4;
 309               tzr->n = 1;
 310               tzr->d = 0;
 311             }
 312           else
 313             {
 314               tzr->m = 10;
 315               tzr->n = 5;
 316               tzr->d = 0;
 317             }
 318         }
 319       else
 320         return;
 321
 322       if (*tz != '\0' && *tz != '/' && *tz != ',')
 323         return;
 324       else if (*tz == '/')
 325         {
 326           /* Get the time of day of the change.  */
 327           ++tz;
 328           if (*tz == '\0')
 329             return;
 330           switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
 331             {
 332             default:
 333               hh = 2;           /* Default to 2:00 AM.  */
 334             case 1:
 335               mm = 0;
 336             case 2:
 337               ss = 0;
 338             case 3:
 339               break;
 340             }
 341           for (l = 0; l < 3; ++l)
 342             {
 343               while (isdigit (*tz))
 344                 ++tz;
 345               if (l < 2 && *tz == ':')
 346                 ++tz;
 347             }
 348           tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
 349         }
 350       else
 351         /* Default to 2:00 AM.  */
 352         tzr->secs = 2 * 60 * 60;
 353
 354       tzr->computed_for = -1;
 355     }
 356
 357   __tzset_run = 1;
 358 }
 359 \f
 360 /* Maximum length of a timezone name.  __tz_compute keeps this up to date
 361    (never decreasing it) when ! __use_tzfile.
 362    tzfile.c keeps it up to date when __use_tzfile.  */
 363 size_t __tzname_cur_max;
 364
 365 long int
 366 __tzname_max ()
 367 {
 368   if (! __tzset_run)
 369     __tzset ();
 370
 371   return __tzname_cur_max;
 372 }
 373 \f
 374 /* Figure out the exact time (as a time_t) in YEAR
 375    when the change described by RULE will occur and
 376    put it in RULE->change, saving YEAR in RULE->computed_for.
 377    Return nonzero if successful, zero on failure.  */
 378 static int
 379 compute_change (rule, year)
 380      tz_rule *rule;
 381      int year;
 382 {
 383   register time_t t;
 384   int y;
 385
 386   if (year != -1 && rule->computed_for == year)
 387     /* Operations on times in 1969 will be slower.  Oh well.  */
 388     return 1;
 389
 390   /* First set T to January 1st, 0:00:00 GMT in YEAR.  */
 391   t = 0;
 392   for (y = 1970; y < year; ++y)
 393     t += SECSPERDAY * (__isleap (y) ? 366 : 365);
 394
 395   switch (rule->type)
 396     {
 397     case J1:
 398       /* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
 399          In non-leap years, or if the day number is 59 or less, just
 400          add SECSPERDAY times the day number-1 to the time of
 401          January 1, midnight, to get the day.  */
 402       t += (rule->d - 1) * SECSPERDAY;
 403       if (rule->d >= 60 && __isleap (year))
 404         t += SECSPERDAY;
 405       break;
 406
 407     case J0:
 408       /* n - Day of year.
 409          Just add SECSPERDAY times the day number to the time of Jan 1st.  */
 410       t += rule->d * SECSPERDAY;
 411       break;
 412
 413     case M:
 414       /* Mm.n.d - Nth "Dth day" of month M.  */
 415       {
 416         register int i, d, m1, yy0, yy1, yy2, dow;
 417         register const unsigned short int *myday =
 418           &__mon_yday[__isleap (year)][rule->m];
 419
 420         /* First add SECSPERDAY for each day in months before M.  */
 421         t += myday[-1] * SECSPERDAY;
 422
 423         /* Use Zeller's Congruence to get day-of-week of first day of month. */
 424         m1 = (rule->m + 9) % 12 + 1;
 425         yy0 = (rule->m <= 2) ? (year - 1) : year;
 426         yy1 = yy0 / 100;
 427         yy2 = yy0 % 100;
 428         dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
 429         if (dow < 0)
 430           dow += 7;
 431
 432         /* DOW is the day-of-week of the first day of the month.  Get the
 433            day-of-month (zero-origin) of the first DOW day of the month.  */
 434         d = rule->d - dow;
 435         if (d < 0)
 436           d += 7;
 437         for (i = 1; i < rule->n; ++i)
 438           {
 439             if (d + 7 >= myday[0] - myday[-1])
 440               break;
 441             d += 7;
 442           }
 443
 444         /* D is the day-of-month (zero-origin) of the day we want.  */
 445         t += d * SECSPERDAY;
 446       }
 447       break;
 448     }
 449
 450   /* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
 451      Just add the time of day and local offset from GMT, and we're done.  */
 452
 453   rule->change = t + rule->offset + rule->secs;
 454   rule->computed_for = year;
 455   return 1;
 456 }
 457
 458
 459 /* Figure out the correct timezone for *TIMER and TM (which must be the same)
 460    and set `__tzname', `__timezone', and `__daylight' accordingly.
 461    Return nonzero on success, zero on failure.  */
 462 int
 463 __tz_compute (timer, tm)
 464      time_t timer;
 465      const struct tm *tm;
 466 {
 467   if (! __tzset_run)
 468     __tzset ();
 469
 470   if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
 471       ! compute_change (&tz_rules[1], 1900 + tm->tm_year))
 472     return 0;
 473
 474   __daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
 475   __timezone = tz_rules[__daylight ? 1 : 0].offset;
 476   __tzname[0] = (char *) tz_rules[0].name;
 477   __tzname[1] = (char *) tz_rules[1].name;
 478
 479   {
 480     /* Keep __tzname_cur_max up to date.  */
 481     size_t len0 = strlen (__tzname[0]);
 482     size_t len1 = strlen (__tzname[1]);
 483     if (len0 > __tzname_cur_max)
 484       __tzname_cur_max = len0;
 485     if (len1 > __tzname_cur_max)
 486       __tzname_cur_max = len1;
 487   }
 488
 489   return 1;
 490 }
 491 \f
 492 #include <libc-lock.h>
 493
 494 /* This locks all the state variables in tzfile.c and this file.  */
 495 __libc_lock_define (, __tzset_lock)
 496
 497 /* Reinterpret the TZ environment variable and set `tzname'.  */
 498 #undef tzset
 499
 500 void
 501 #ifdef weak_function
 502 weak_function
 503 #endif
 504 tzset (void)
 505 {
 506   __libc_lock_lock (__tzset_lock);
 507   __tzset ();
 508   __libc_lock_unlock (__tzset_lock);
 509 }